@Dbug: Yes, currently I have OSDK and CC65 working side-by-side. I'm using common Makefile per project, so it's easy to compile everything with both toolchains. And yes, CC65 seams to be actively developped (unfortunately most changes are related to Commodore).
I hope to have GCC as an option soon too, but for now I succeeded only in building the compiler. My checks with dejagnu regression tests are far from the announced on the maintainer's site. I'm waiting his feedback.
Attached is aes256 demo compiled with CC65 with preprocessed files (look for *.c1 files )